1. True. Residues such as Glu, Cys, Thr, Ser, and Asn can cause destabilization of alpha-helixes, so the spacing of the residues are critical. The spacing and the intermolecular interaction caused by the spacing seem correct, so this could be a likely repeat in the alpha-helix of keratin. However, I am not 100% positive.

2. False. This could be true, but I believe that it is false. From my understanding, each polypeptide in a dimer has 3.6 residues/turn not 3.5.

3. True. If they are in contact with the solvent, which assuming is a polar solvent then they are likely to be polar residues.

4. False. The strength is due to hydrogen bonding and hydrophobic interactions

5. False. Look at 1 for an explanation.

6. False. Studies have shown that it is wound more tightly then predicted.

7. True. Cys residues are abundant in alpha-keratin, but they are not in such numbers as the hydrophobic residues found in alpha-keratin. Cys residues allow for covalent disulfide bonds for the formation of profilaments for strength, but the close packing between two-chain coils that make them insoluble and hard is due to the intermolecular hydrogen bonding, not covalent disulfide bonds, but they are responsible for covalent cross-links between peptide chains, which increase the strength of the protein.